It is known that exterior lightning protection devices alone are not sufficient to prevent damage to interior electrical equipment when lightning strikes. Excess currents may still be generated in electronic and electrical devices inside a building, vehicle, or craft such as an aircraft. Thus, steps must be taken against the effects of currents caused by lightning and against the resulting magnetic and electrical fields generated on interior metal installations and electrical equipment. The most important step in this connection is an efficient and rapid potential equalization by grounding to avoid thunderstorm electrical damages. Such equalization is accomplished by an effective electrical grounding connection of the endangered equipment to grounded metallic pipes or other grounding devices, if necessary through spark gap arresters. Such grounding connections must permit a rapid connection and disconnection of two couplings with each other and at least one of the couplings with a grounding conductor while assuring an effective equalization of any excess electrical potential caused by lightning.
Several versions of such grounding connectors are known for realizing the grounding of lightning protection systems. Normally, one end of a grounding conductor is secured to a metal cable clamp which in turn is connected to the component to be protected while the other end of the grounding conductor is secured to a grounded pipe system or the like. Such cable clamps have also been secured to cable end connectors and cable couplings, including an end housing that itself is connected to an electrically conducting, protective cable envelope or cable casing, such as a wire mesh cable envelope. The use of cable clamps for these purposes is cumbersome, at least in those instances where it is not possible to place the cable clamp around the cable end housing or around a sleeve extending from the end housing due to lack of accessibility. Even if the grounding conductor can be secured to the cable clamp by a screw connection, the placement of the cable clamp itself is cumbersome. Thus, efforts have been made to provide divided cable clamps that can be placed around a cable even if there is no free cable end. However, such divided cable clamps still require a connector and a sleeve for securing the divided cable clamp.
In addition to the mechanical difficulties of properly placing a cable clamp or even a divided cable clamp, the conventional devices have the disadvantage that transition resistances occur between the cable clamp and the component to which the cable clamp is secured. Further, corrosion tends to start between the clamp and the sleeve or end housing to which the clamp is secured. Besides, the clamp itself requires an additional expense for making these separate clamps and the combined weight of a multitude of clamps can be substantial, thereby adding to the weight of the system.
German Patent Publication 118,849 (Dunkel), published on Dec. 7, 1961, discloses a cable coupling comprising a male cable terminal and a female cable terminal. The female terminal is provided with a grounding sleeve also referred to as screen or shielding sleeve. One end of the grounding sleeve is connected with a coupling sleeve. The other end of the grounding or shielding sleeve is provided with contact tongues that are circumferentially distributed around the grounding or shielding sleeve. The contact tongues are preferably spring contacts which bear against the screen casing of the high frequency cable. Each contact tongue contributes to a transition resistance established between the respective contact tongue and the surface of the screen or wire mesh cable casing. Further, the tongues are subject to contamination and corrosion, which contribute to increasing the transition resistance over time, whereby the desired grounding capability deteriorates. Dunkel does not make any suggestion to constructing a coupling sleeve of a cable terminal and a grounding sleeve as a single-piece electrical conductor.